Refactor EvalWeight to add weight field array

A few things here:
- Getting rid of namespace std, to respect code convetions. At the same
time, using cout for warning instead of cerr so they do not appear as
errors in Slicer.

- Add PrintDebug flag to prevent from printing out message during normal
execution.

- Actually print an output file with the weights fiels arrays

- Handle LPS<->RAS better

See Issue #13931
Big PoseBody Refactoring

Refactor Pose Body to be able to handle input sufarces that have weight
field arrays. This will greatly improve perfomances as there is no need
in processing the input weight images anymore. It is however still possible
to use a surface without these field arrays

See Issue #13931
Merge branch '13931-RealTimePoseBody' into heat-diffusion

* 13931-RealTimePoseBody:
  Big PoseBody Refactoring
  Refactor EvalWeight to add weight field array